mirror of
https://github.com/AuxXxilium/linux_dsm_epyc7002.git
synced 2024-11-24 18:41:00 +07:00
f68e148050
When the mm being switched to matches the active mm, we don't need to increment and then drop the mm count. In a simple benchmark this happens in about 50% of time. Making that conditional reduces contention on that cacheline on SMP systems. Acked-by: Andrea Arcangeli <aarcange@redhat.com> Signed-off-by: Michael S. Tsirkin <mst@redhat.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
59 lines
1.3 KiB
C
59 lines
1.3 KiB
C
/* Copyright (C) 2009 Red Hat, Inc.
|
|
*
|
|
* See ../COPYING for licensing terms.
|
|
*/
|
|
|
|
#include <linux/mm.h>
|
|
#include <linux/mmu_context.h>
|
|
#include <linux/sched.h>
|
|
|
|
#include <asm/mmu_context.h>
|
|
|
|
/*
|
|
* use_mm
|
|
* Makes the calling kernel thread take on the specified
|
|
* mm context.
|
|
* Called by the retry thread execute retries within the
|
|
* iocb issuer's mm context, so that copy_from/to_user
|
|
* operations work seamlessly for aio.
|
|
* (Note: this routine is intended to be called only
|
|
* from a kernel thread context)
|
|
*/
|
|
void use_mm(struct mm_struct *mm)
|
|
{
|
|
struct mm_struct *active_mm;
|
|
struct task_struct *tsk = current;
|
|
|
|
task_lock(tsk);
|
|
active_mm = tsk->active_mm;
|
|
if (active_mm != mm) {
|
|
atomic_inc(&mm->mm_count);
|
|
tsk->active_mm = mm;
|
|
}
|
|
tsk->mm = mm;
|
|
switch_mm(active_mm, mm, tsk);
|
|
task_unlock(tsk);
|
|
|
|
if (active_mm != mm)
|
|
mmdrop(active_mm);
|
|
}
|
|
|
|
/*
|
|
* unuse_mm
|
|
* Reverses the effect of use_mm, i.e. releases the
|
|
* specified mm context which was earlier taken on
|
|
* by the calling kernel thread
|
|
* (Note: this routine is intended to be called only
|
|
* from a kernel thread context)
|
|
*/
|
|
void unuse_mm(struct mm_struct *mm)
|
|
{
|
|
struct task_struct *tsk = current;
|
|
|
|
task_lock(tsk);
|
|
tsk->mm = NULL;
|
|
/* active_mm is still 'mm' */
|
|
enter_lazy_tlb(mm, tsk);
|
|
task_unlock(tsk);
|
|
}
|